nobikes

I have recently purchased a class set of the Arduino Boards for my High School Engineering class. The programing is very simple for the students to understand. My end game is to use the chips for simple robotics. But before that i want to make a simple 10 LED display that the students can take home for cheap.

The Idea is that students program the chip then remove it and plug it in to their light display. Has any one done this before?

If not, I need to know a few basics.

Which pins hook up to the timing crystal?

What is the spec on the crystal?

Can the Arduino run on 9V? (Simple battery clips make 9V perfect)

Any way, i probably have more questions, But any input at this point would be great. 8-)

jluciani

The specification for the crystal depends on the input voltage. For a 5V system most people use a 16MHz. For my 12V boards I use12MHz. The ATmel specification recommends loading capacitanceof 22pF or less.

The 9V battery can power a 5V system but it is not very efficient. Most systems use a linear regulator which wastes 4/9 of the capacity.

I make a low-cost ($12) Arduino compatible board (PICO1TR) and a matching LED matrix. You can check out the schematics which are in the datasheets.I "charlie-plex" the LEDs which minimizes the number of lines required.For 10 LEDs you would only need 4 lines. See the datasheets at http://wiblocks.luciani.org/PICO/PICO1TR-index.htmland http://wiblocks.luciani.org/PICO/PICO1TR-LED-L-index.html

(* jcl *)

nobikes

Okay, i think i know what i am doing. a few more questions though. Is the pin configuration on The Atmega 168 the same as the 328? The price of the 168 is cheaper then the 328, will the 168 work if i plug it in to my Duemilanove board? Do I need a voltage regulator if i run 4.5volts from a pack of 3 AA batteries? I have attached a Schematic of what i think will work. does any one see a problem with it?

Yes but change the board type in the tools menu.Remember you have to have a boot loader in the chip before you plug it in the board. Chips can either be bought with a boot loader ready loaded otherwise you are going to have to burn one in yourself with a programmer.

assuming 1.7V drop across each LED the across the resistor you have 5 - 1.7 = 3.3 voltsacross a 220R resistor gives you 15mA per LED.With 14 LEDs you have a total source current of:-14 * 15mA = 210mA

Now the absolute limit for the current taken along the arduino supply pins is 200mA. Given it takes about 20mA to power the chip you are 30mA over the current where damage would be done.So best bet is just to up the resistors a tad say to 270R.